A retrovirus designated human immunodeficiency virus (HIV) is the etiological agent of the complex disease that includes progressive destruction of the immune system (acquired immune deficiency syndrome, hereinafter AIDS) and degeneration of the central and peripheral nervous system. There are two types of HIV, HIV-1 and HIV-2, the latter producing a less severe disease than the former. Being a retrovirus, its genetic material is in the form of RNA (ribonucleic acid) consisting of two single RNA strands. Coexisting with RNA are reverse transcriptase (having polymerase and ribonuclease activity), integrase, a protease and other proteins.
It is known in the art that some antiviral compounds which act as inhibitors of HIV replication are effective agents in the treatment of AIDS and similar diseases. Drugs that are known and approved for the treatment of HIV-infected patients belong to one of the following classes:                nucleoside reverse transcriptase (RT) inhibitors such as, but not limited to, azidothymidine (AZT), and lamivudine (3TC),        nucleotide reverse transcriptase inhibitors such as, but not limited to, tenofovir (R-PMPA),        non-nucleoside reverse transcriptase inhibitors such as, but not limited to, nevirapine, efavirenz,        protease inhibitors such as, but not limited to, nelfinavir, saquinavir, ritonavir and amprenavir,        fusion inhibitors such as enfuvirtide, and        integrase inhibitors such as raltegravir or elvitegravir.        
Replication of the human immunodeficiency virus type 1 (hereinafter referred as HIV-1) can be drastically reduced in infected patients by combining potent antiviral drugs targeted at multiple viral targets, as reviewed by Vandamme at al. in Antiviral Chem. Chemother. (1998) 9:187-203.
Multiple-drug combination regimes can reduce viral load below the detection limit of the most sensitive tests. Nevertheless low level ongoing replication has been shown to occur, possibly in sanctuary sites, leading to the emergence of drug-resistant strains, according to Perelson et al. in Nature (1997) 387:123-124. Furthermore the selectivity of many antiviral agents is rather low, possibly making them responsible for side-effects and toxicity. Moreover, HIV can develop resistance to most, if not all, currently approved antiviral drugs, according to Schmit at al. in J. Infect. Dis. (1996) 174:962-968. It is well documented that the ability of HIV to rapidly evolve drug resistance, together with toxicity problems resulting from known drugs, requires the development of additional classes of antiviral drugs.
As a summary, there is still a stringent need in the art for potent inhibitors of HIV. Therefore a goal of the present invention is to satisfy this urgent need by identifying efficient pharmaceutically active ingredients that are active against HIV, less toxic, more stable (i.e. chemically stable, metabolically stable), effective against viruses resistant to currently available drugs and/or which are more resistant to virus mutations than existing antiviral drugs and that can be useful, either alone or in combination with other active ingredients, for the treatment of retroviral infections, in particular lentiviral infections, and more particularly HIV infections, in mammals and more specifically in humans. It is also known to the skilled in the art that the physicochemical properties of known drugs as well as their ADME-Tox (administration, distribution, metabolism, excretion) properties may limit or prohibit their use in the treatment of diseases. Therefore, a problem of existing drugs that can be overcome with the compounds of the invention can be selected from a poor or inadequate physicochemical or ADME-Tox properties such as solubility, Log P, CYP inhibition, hepatic stability, plasmatic stability, among others have been taken into account in the design and the synthesis of the compounds of the present invention. Furthermore, another goal of the present invention is to complement existing antiviral drugs in such a way that the resulting drug combination has improved activity or improved resistance to virus mutation than each of the individual compounds.
The prior art describes a small number of thieno[2,3-b]pyridines with a structure similar to the thieno[2,3-b]pyridines of the invention, but no medical use is known for these compounds.